1. Field of the Invention
This invention relates to a gun for producing adhesive foam, and more particularly, to a gun with a nozzle tube, a delivery lever, and a nozzle needle arranged coaxially in the nozzle tube.
2. Discussion of Relevant Art
Such a device is known, for example, from German Patent DE 44 12 282.
When the adhesive foam can is screwed on, the fluid under pressure is present in a cavity and in the nozzle tube of the gun. Passing through the cavity and nozzle tube is a nozzle needle which in its closing position seals off the outlet opening of the nozzle tube. When the delivery lever is pulled, the nozzle needle is pulled out of its closing position, and the fluid under pressure can emerge from the outlet opening. The cavity is bounded by a wall section which has a bore in which is arranged the guide means for guiding the nozzle needle.
In the known guns, the guiding is effected by a bore in the wall section. So that the fluid under pressure does not get out into the housing space of the gun and in the course of time render inoperative the coupling device between the delivery lever and the nozzle needle, and also further elements located in the housing of the gun, two lip seals for sealing the needle are provided in the known guns on the side of the guide remote from the cavity.
In these known guns a sufficient sealing is indeed attained. However, the production and materials costs are disadvantageous here, as are the difficulties which arise when the seal becomes damaged.